This invention relates to an expansion anchor.
Expansion anchors with an anchor bolt, an expansion body, action means and an expansion sleeve surrounding the anchor bolt are used to fasten workpieces to a structural component. For this purpose, a boring is worked into the structural component which can be, for example, a concrete wall or a concrete ceiling, and then the anchor bolt is inserted into the boring. With the action means, the conical expansion body on the anchor bolt is moved so that the expansion body thereby presses the expansion sleeve radially outward resulting in an anchoring of the expansion bolt as a result of radial forces between the expansion sleeve or the expansion body and the structural component, such as the concrete that surrounds the boring. Workpieces or other items can thereby be fastened to the expansion anchor.
Between the expansion anchor and the wall of the borehole, a friction force between the wall of the borehole in the structural component and the expansion sleeve effects the anchoring of the expansion anchor. The conical expansion bodies are rotationally symmetrical to a longitudinal axis of the anchor bolt or of the expansion body.
German Patent Document No. DE 41 16 149 A1 describes an expansion anchor with anchor bolts, the cylindrical shank of which has an expanded portion in a terminal portion in the direction of installation, and on the end farther from this expanded portion has action means to bear the load, whereby the anchor bolt is surrounded at least along a portion of its shank by an expansion sleeve that can be displaced relative to the anchor bolt and has at least one longitudinal slot that is open toward the installation-side end and is provided with radial projections on its external contour.
The object of this invention is therefore to make available an expansion anchor in which a solid connection between the anchor sleeve and the concrete can be achieved with low manufacturing costs of the expansion anchor.
This object is accomplished with an expansion anchor that comprises an anchor bolt with an expansion body on a first terminal section of the anchor bolt with a longitudinal axis, at least one action means on another, second terminal section of the anchor bolt to bear the load, an expansion sleeve that surrounds the anchor bolt, whereby the expansion body, on the radially outer side, is at different distances from the longitudinal axis with reference to at least one identical point on the longitudinal axis in a transfer zone.
The expansion body of the anchor bolt therefore does not have a rotationally symmetrical geometry with reference to the longitudinal axis of the anchor bolt. Compared to a rotationally symmetric geometry, on one hand the invention teaches that the tendency of the cone to damage the borehole when it is hammered into the borehole is reduced, so that, according to the invention the energy required for installation and in particular the number of hammer blows required can be reduced. In addition, on account of the design of the conical shape of the invention, a co-rotation of the bolt during the application of the installation torque is reduced. During the spreading or radially outward deformation of the expansion sleeve with the expansion body, on the other hand, different deformations or expansions of the expansion sleeve occur in the tangential direction on the expansion body. As a result, the expansion sleeve or the expansion body can dig into the borehole wall or spread apart in a structural component with a very high compression force on the wall of the borehole in spot locations, as a result of which particularly large forces can thereby be absorbed by the expansion anchor. As a result of this geometry of the expansion body, manufacturing tolerances have only a very slight influence on the forces that can be transmitted to the wall of the borehole by the expansion anchor, so that reduced manufacturing precision in the manufacture of the expansion body is sufficient, which makes it possible to reduce manufacturing costs.
In particular, at least the transfer zone is corrugated or serrated, for example with at least 3, 4 or 7, preferably 7 to 9, corrugations or serrations and/or the distances between the at least one point and the longitudinal axis differ by at least 1%, 2%, 3%, 4%, 5%, 10%, 15% or 20%. The corrugations are preferably rounded by radii on their radial outside peaks. The serrations, on the other hand, can have angled edges.
In an additional configuration, the corrugated or serrated transfer zone occupies only a portion of the expansion body in the axial direction. Alternatively, the entire expansion body can be provided with corrugations or serrations.
The expansion body, in particular outside the transfer zone, has a conical geometry.
In an additional embodiment, the transfer zone has an essentially cylindrical shape and a longitudinal axis of the cylinder is oriented coaxially with the longitudinal axis of the anchor bolt. On account of the cylindrical transfer zone, the expansion body does not have a conical shape in the transfer zone. Therefore when the expansion sleeve with the expansion body is expanded, first of all the expansion sleeve on the conical expansion body expands radially outside the transfer zone and only in the vicinity of a first rear end of the anchor bolt does the transfer zone occur. At the beginning of the transfer zone, on account of the corrugated or serrated geometry of the transfer zone, as well as, in the transfer zone, different distances occur between the longitudinal axis and the transfer zone. Consequently, at the conclusion of the expansion process, the expansion anchor will be radially expanded to different degrees. The result can be a particularly effective anchoring of the expansion sleeve or of the expansion body in a borehole wall of a structural component such as a concrete wall or a concrete ceiling. Particularly high friction forces can therefore be transmitted on account of the high friction forces that occur in spot locations, and a positive or form-fitting anchoring of the expansion sleeve and/or of the expansion body in the borehole wall can be achieved.
Alternatively, the transfer zone can be essentially conical, whereby the apex angle of the transfer zone is preferably smaller than the apex angle of the expansion body outside the transfer zone. The expansion body preferably has two conical areas with different apex angles, whereby one of these areas contains the transfer zone with the corrugations or serrations.
Preferably, in a cross-section of the transfer zone, the points of the transfer zone which are at a maximum distance from the longitudinal axis are connected by a virtual circumscribed circle and the center of the circle corresponds to the longitudinal axis and/or in a cross-section of the transfer zone, the points of the transfer zone which are at a minimum distance to the longitudinal axis are connected with a virtual inscribed circle and the center of the inscribed circle corresponds to the longitudinal axis.
Conventional expansion bodies described in the prior art are rotationally symmetrical to the longitudinal axis. In one variant, the expansion body outside the transfer zone is conical or in the shape of a truncated cone and in the transfer zone the virtual inscribed circle and/or circumscribed circle has an essentially constant radius, i.e., the transfer zone is essentially cylindrical. The radius of the virtual circumscribed circle is greater than the maximum distance on the radial outside from the longitudinal axis of an expansion body described in the prior art. In one application of a rotationally symmetrical expansion body described in the prior art, the expansion sleeve, on account of the size or the geometry of the expansion sleeve, is associated with a specified expansion body and the maximum distance of this rotationally symmetrical expansion body known from the prior art is therefore smaller than the radius of the circumscribed circle. Consequently, during the expansion of the expansion body, when the expansion anchor claimed by the invention is used, it expands locally and radially to a greater extent at points that are at a maximum distance from the longitudinal axis than with the use of an expansion body described in the prior art. The radius of the inscribed circle is therefore less than or essentially equal to, i.e., with a variance of 10%, 5%, 3%, 2% or 1%, the maximum radius or the maximum distance from the longitudinal axis on the expansion body described in the prior art. In particular, the radius of the circumscribed circle can be different by at least 1% from the radius of the inscribed circle. As a result, with the use of an expansion body claimed by the invention, the expansion body is also expanded radially to a lesser extent or to an essentially equal extent at the points that are at a minimum distance from the longitudinal axis.
The radius of the virtual circumscribed circle advantageously varies by less than 20%, 10% or 5% and/or the radius of the virtual inscribed circle varies by less than 20%, 10% or 5%.
In an additional embodiment, the at least one action means comprises a thread on the anchor bolt, a shim or a baseplate with a boring and a nut.
In particular, the at least one action means is on a second terminal section of the anchor bolt.
In an additional embodiment, the anchor bolt and/or the expansion body and/or the at least one action means are made at least partly or completely of metal, such as steel, for example.
In an additional embodiment, the anchor bolt has a support ring and the expansion body is supported on the support ring. When the anchor bolt is unscrewed with the action means, e.g., the nut, an axial fastening of the expansion sleeve is necessary so that the expansion sleeve can expand. This expansion is accomplished by means of a frictional connection, e.g., because the expansion sleeve is additionally provided with projections.
In an additional variant of the invention, the expansion sleeve is guided up to a shim, i.e., it is in contact with an action means, and when the anchor bolt is unscrewed, the axial fixing of the expansion sleeve is not provided by friction between the borehole wall and the expansion sleeve but as a result of the fact that the expansion sleeve is in contact with at least one action means, e.g., a shim.
One exemplary embodiment of the invention is described in greater detail below with reference to the accompanying figures.